send slack notification on unit test failure (vechain#667)

* slack notification

* code review

.github/workflows/test.yaml

@@ -1,6 +1,14 @@
 name: Unit Tests
 
-on: [push, pull_request]
+on: 
+  push:
+    branches:
+      - 'master'
+      - 'master-*'
+
+  pull_request:
+    branches:
+      - master
 
 jobs:
   unit_tests:
@@ -27,7 +35,22 @@ jobs:
         run: make all
 
       - name: Make Test
+        id: unit-test
         run: make test
+
+      - name: Post To Slack
+        if: always()  && github.ref == 'refs/heads/master' && (steps.unit-test.outcome == 'failure')
+        uses: slackapi/[email protected]
+        with:
+          payload: |
+            {
+              "source": "GitHub",
+              "repo": "${{ github.repository}}",
+              "branch": "${{ github.head_ref || github.ref_name }}",
+              "message": "unit tests failed on ${{ matrix.os }} with go version ${{ matrix.go-version }}"
+            }
+        env:
+          SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK_URL }}
   test_coverage:
     runs-on: ubuntu-latest 
     steps: